CN101326300B - Hot-dip zinc-coated steel sheets and process for production thereof - Google Patents

Hot-dip zinc-coated steel sheets and process for production thereof Download PDF

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CN101326300B
CN101326300B CN200680046556.8A CN200680046556A CN101326300B CN 101326300 B CN101326300 B CN 101326300B CN 200680046556 A CN200680046556 A CN 200680046556A CN 101326300 B CN101326300 B CN 101326300B
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CN101326300A (en
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木村英之
小野义彦
藤田毅
二塚贵之
松冈才二
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JFE Engineering Corp
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NKK Corp
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0426—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0436—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
    • C23C2/0224—Two or more thermal pretreatments
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • C23C2/29—Cooling or quenching
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

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  • Chemical Kinetics & Catalysis (AREA)
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Abstract

A galvanized steel sheet excellent in strength-ductility balance and bake-hardenability as well as a method for producing the same are provided. The chemical components thereof include C, Si, Mn, P, S, Al, N and Cr at content ratios of 0.005 to 0.04%, 1.5% or lower, 1.0 to 2.0%, 0.10% or lower, 0.03% or lower, 0.01 to 0.1%, less than 0.008% and 0.2 to 1.0%, respectively, with Mn (mass%) + 1.29Cr (mass%) being in the range of 2.1 to 2.8, and further include iron and unavoidable impurities as the balance. The structure thereof consists of a ferrite phase and a martensite phase with a volume fraction being at least 3.0% and less than 10%, the average particle diameter of the ferrite is larger than 6 [mu]m and not more than 15 [mu]m, and 90% or more of the martensite phase exists in a ferritegrain boundary. In addition, in the production process of such a galvanized steel sheet, a steel sheet obtained in a cold rolling step is annealed at a temperature being at least the Ac1 point and not more than the Ac3 point.

Description

Hot-dip galvanizing sheet steel and manufacture method thereof
Technical field
The present invention relates to a kind ofly be applicable to fields such as automobile, household electrical appliances, and press formability is good, balance and good hot-dip galvanizing sheet steel and the manufacture method thereof of sintering curing of intensity and ductility.
Background technology
In recent years, need improve oil consumption from the viewpoint of the environment of preserving our planet, and protection steward's viewpoint needs to improve the security of car body when colliding from vehicle.In order to satisfy such requirement, the research that is used for realizing the lightweight of car body and strengthening two aspects is actively developed.For the lightweight of satisfying car body simultaneously and the requirement of reinforcement, it is effective making the former material high strength of parts.But, because the raising of intensity causes the plasticity variation easily, therefore under the situation of the autobody sheet that needs complicated processing, also require good press formability when requiring high strength.
According to above-mentioned situation, various tests have been carried out in order when guaranteeing the processibility of steel plate, to realize high strength all the time.Particularly formed by to as heavy addition solution strengthening elements Si, P in the IF steel of base material, thereby guaranteed the method for the tensile strength of 340～490MPa.For example, in patent documentation 1, disclose to the Production Example that adds the high tensile steel plate of the tensile strength 490MPa level behind the interpolation P in the Ti ultra-low carbon steel.
And, for high working property and the high strength of taking into account steel plate, the complex tissue steel plate that generates hard second phases such as martensite or bainite in the ferrite subject organization is studied.For example, in patent documentation 2, following method is disclosed: in the steel plate of tissue by ferrite and second phase composite, by 500～700 ℃ temperature range is made as during until annealing temperature in heating 10 ℃/suppress the recovery of ferritic worked structure more than the s, and the ferrite particle diameter is fine to turn to the hard second mutually fine dispersion that 2～6 μ m make becomes the fracture starting point by making, thereby the steel plate that obtains having the balance of intensity good about 17000MPa*% and ductility.And, in patent documentation 3 and 4, following method is disclosed: organizing by ferrite and containing in the steel plate of martensitic second phase composite, by the speed of cooling behind the regulation recrystallization, and control the mark of second phase and martensite second mutually in shared ratio, thereby obtain having the following intensity of 500MPa and the steel plate with balance of intensity good about 17000MPa*% and ductility.
And, as the high-intensity steel plate after can satisfying good press formability simultaneously and being shaped, developed before the drawing more soft and be easy to shaping, improve strength of parts thereby can handle to be cured by coating sintering after the drawing, and have the steel plate of sintering curing (below be sometimes referred to as BH) property.This BH steel plate is the technology that makes its curing by the strain aging phenomenon of utilizing solid solution C, N, for example, in patent documentation 5, disclose by solid solution C about 30ppm is present in the ferritic structure in order to pinned dislocation, thereby improved the steel plate of sintering curing.And the steel plate of record is used as automobile exterior panel panel in the past in this patent documentation 5.But above-mentioned steel plate solid solution C amount originally is few, so the BH amount is only about 30～50MPa.And, since with ultra-low carbon steel as base material, thereby be difficult to guarantee the strength of parts that 440MPa is above.To this, from obtaining the viewpoint of high BH, to by introducing dislocation in the martensitic phase break-in parent phase ferrite, making solid solution C in the ferrite because pinned dislocation and the complex tissue steel plate that can give high BH is studied.For example, in patent documentation 6, following method is disclosed: be in 1.3～2.1% the steel as Mn, the Cr of one of index of hardenability and the weighting total amount of Mo: Mn+1.29Cr+3.29Mo, by making steel plate organize rate by volume to count ferrite more than 70% and 1～15% martensite, thus the steel plate that obtains having the intensity of 440～640MPa and have the above high BH amount of 60MPa.
Patent documentation 1: Japanese Patent Publication 57-57945 communique
Patent documentation 2: TOHKEMY 2002-235145 communique
Patent documentation 3: TOHKEMY 2002-322537 communique
Patent documentation 4: TOHKEMY 2001-207237 communique
Patent documentation 5: Japanese kokai publication sho 59-31827 communique
Patent documentation 6: TOHKEMY 2006-233294 communique
But there is problem as described below in above-mentioned prior art.
For example, the technology of record has to depend on solution strengthening as strengthening mechanism in patent documentation 1 and the patent documentation 5 aspect the propelling high strength.For example, in order to ensure the intensity more than the 440MPa, need to add a large amount of Si, P, thereby difficult alloying and red rust, surface texture such as do not plate and become problem.Thereby be difficult to be applied to be strict with especially the automobile exterior panel panel use of surface quality.
And, the technology of record is made as 2～6 μ m with the ferrite median size in the patent documentation 2, but because the miniaturization of ferrite particle diameter is accompanied by the reduction of n value and uniform elongation, so be difficult to be applied to automobile exterior panel panel part materials such as door, hood based on stretch forming.The second shared ratio raising of middle martensite mutually in the technology of record in patent documentation 3 and the patent documentation 4, therefore in its manufacturing processed, a speed of cooling from annealing temperature to the plating temperature is made as 1～10 ℃/s, and then in order to make second below 10%, is preferably 1～3 ℃/s.But, in order to make second phase fraction below 10%, when a speed of cooling from annealing temperature to the plating temperature is made as 1～3 ℃/s, for example, as be shown in the examples, when from 800 ℃ of annealing temperatures to the plating temperature 460 ℃ with 3 ℃ of speed of cooling/when s cools off, need about 113s, thereby worry productivity reduces.And, embodiment (patent documentation 3 according to record in the patent documentation 3,4, embodiment in the specification sheets, sample No.43 and patent documentation 4, the embodiment in the specification sheets, sample No.29), when being 2.15 steel to Mn+1.3Cr with 3 ℃ of speed of cooling/when s cools off, the phase transformation of perlite or bainite has taken place in the result to little tissue is estimated in the cooling, thereby is difficult to make second stable being in more than 90% of ratio of martensite in mutually.The result uses composition and the manufacture method of record in the patent documentation 3 or 4 as can be known thus, might owing to second in mutually perlite or bainite separate out the reduction that causes ductility, thereby be difficult to stably obtain the good steel plate of balance of intensity and ductility.
For the technology of record in the patent documentation 2～4, make plate with the former material of the GA of 0.6～0.8mmt according to embodiment, the opposite house model carries out punching test, and result's grade around difficult slightly shaping is embossing has produced crackle.Therefore, by the result who measures the former material characteristic that represents as can be known, TS:443MPa, El:35.5%, TS * El:15727MPa*% are so the balance of intensity and ductility may not be good.As this reason, the thickness of slab that steel plate is discussed among the embodiment of record in patent documentation 2～4 is 1.2mm, thereby thinks that the balance of intensity and ductility is good owing to the thickness of slab effect.Therefore, when the different steel-sheet ductility of thickness of slab is estimated, use with the Oliver formula shown in the widely used following formula of those skilled in the art (1) (source: drawing difficulty or ease handbook-Di 2 editions-, P.458, sheet metal forming technology meeting) following formula (2) that gets for basic conversion is tested.
Figure S2006800465568D00041
λ, m are material constant, and when being iron, m is generally 0.4.A is sectional area, and L is gauge length.
El 2/El 1＝(t 2/t 1) 0.2 (2)
El 1, El 2Be respectively that thickness of slab is t 1(mm), t 2(mm) elongation the time (%).
By this result as can be known, when estimating with a large amount of thickness of slab 0.75mm that are used for the automobile exterior panel panel, embodiment (the embodiment in the specification sheets of record in the patent documentation 2, sample No.35) in, TS:446MPa, El:35.7%, TS * El:15922MPa*%, embodiment (the embodiment in the specification sheets of record in the patent documentation 3, sample No.43) in, TS:441MPa, El:35.6%, TS * El:15700MPa*%, embodiment (the embodiment in the specification sheets of record in the patent documentation 4, sample No.29) in, TS:442MPa, El:35.5%, TS * El:15691MPa*%, intensity is ductility balanced in arbitrary embodiment all may not be good.In addition, from the viewpoint of press formability, think that if TS * El then being level no problem in practicality more than the 16000MPa*%, is preferably 16500MPa*%, be more preferably 17000MPa*%.Therefore, the technology of patent documentation 2～4 is difficult to be applied to automobile exterior panel panel part materials such as door, hood.
And, the technology of record is in order to control the solid solution C amount in martensite mark and the ferrite and to guarantee high BH amount in the patent documentation 6, with cooling temperature be that 100 ℃/s is above, to stop temperature be that condition below 200 ℃ is carried out the secondary cooling in cooling, but in order to satisfy such cooling conditions, need as special method such as quenching in water column of putting down in writing in the patent documentation 6, the industrial production of reality is difficult.And, only record the evaluation of carrying out with cylinder test about plasticity in the patent documentation 6, do not have the record of relevant ductility such as full elongation, uniform elongation and local elongation rate, thereby the balance of intensity and ductility may not be good, is difficult to be applied to automobile exterior panel panel part materials such as door, hood.
Summary of the invention
The present invention finishes in order to address the above problem just, its purpose is, provide tensile strength more than the 340MPa and below 590MPa, viewpoint from press formability, TS * El is more than the 16000MPa*%, from guaranteeing the viewpoint of shock-resistance, after steel plate being applied 2% prestrain, implement the thermal treatment of 170 ℃ * 20min and carry out the hot-dip galvanizing sheet steel of yielding stress difference more than 50MPa that the front and back of sintering processes are measured, namely have high formability, and the hot-dip galvanizing sheet steel that the balance of intensity and ductility and sintering curing are good and manufacture method thereof.
In order to solve above-mentioned problem, the inventor is conceived to the complex tissue of ferritic phase+martensitic phase.The result obtains following conclusion.
At first, by utilizing phase transformation strengthening as strengthening mechanism, the volume fraction of martensitic phase is reduced as far as possible, thereby obtain the strength range of 340～590MPa of being difficult to obtain with the IF steel substrate.
And, by the location of control ferrite particle diameter and martensitic phase, improve ferritic energy of deformation, thereby realize the raising of uniform elongation.
And then, evenly disperse mutually and the local elongation rate is improved by making second, thereby can obtain the good hot-dip galvanizing sheet steel of balance of intensity and ductility.
And then, by suitably controlling the weighting content as Mn, the Cr of one of hardenability index, obtain having the steel plate of high BH amount.
The present invention is based on above conclusion, its main points are as follows:
A kind of hot-dip galvanizing sheet steel, it is characterized in that, having following one-tenth is grouped into: by quality %, contain that C:0.005～0.04%, Si:1.5% are following, Mn:1.0～2.0%, P:0.10% is following, S:0.03% is following, Al:0.01～0.1%, N: less than 0.008% and Cr:0.2～1.0%, and satisfy 2.1≤Mn (quality %)+1.29Cr (quality %)≤2.8, surplus is made up of iron and unavoidable impurities; Tissue by ferritic phase and volume fraction more than 3.0%, the martensitic phase of less than 10% forms, and described ferritic median size surpasses 6 μ m and below 15 μ m, and the ratio that described martensitic phase exists in the ferrite crystal boundary is more than 90%.
A kind of hot-dip galvanizing sheet steel, it is characterized in that, having following one-tenth is grouped into: by quality %, contain that C:0.005～0.04%, Si:1.5% are following, Mn:1.0～2.0%, P:0.10% is following, S:0.03% is following, Al:0.01～0.1%, N: less than 0.008% and Cr:0.2～1.0%, and satisfy 2.2≤Mn (quality %)+1.29Cr (quality %)≤2.8, surplus is made up of iron and unavoidable impurities; Tissue by ferritic phase and volume fraction more than 3.0%, the martensitic phase of less than 10% forms, and described ferritic median size surpasses 6 μ m and below 15 μ m, and the ratio that described martensitic phase exists in the ferrite crystal boundary is more than 90%.
A kind of hot-dip galvanizing sheet steel, it is characterized in that, having following one-tenth is grouped into: by quality %, contain that C:0.005～0.04%, Si:1.5% are following, Mn:1.0～2.0%, P:0.10% is following, S:0.03% is following, Al:0.01～0.1%, N: less than 0.008% and Cr:0.2～1.0%, and satisfy 2.3≤Mn (quality %)+1.29Cr (quality %)≤2.8, surplus is made up of iron and unavoidable impurities; Tissue by ferritic phase and volume fraction more than 3.0%, the martensitic phase of less than 10% forms, and described ferritic median size surpasses 6 μ m and below 15 μ m, and the ratio that described martensitic phase exists in the ferrite crystal boundary is more than 90%.
A kind of hot-dip galvanizing sheet steel, it is characterized in that, having following one-tenth is grouped into: by quality %, contain that C:0.005～0.04%, Si:1.5% are following, Mn:1.0～2.0%, P:0.10% is following, S:0.03% is following, Al:0.01～0.1%, N: less than 0.008% and Cr:0.35～0.8%, and satisfy 2.3≤Mn (quality %)+1.29Cr (quality %)≤2.8, surplus is made up of iron and unavoidable impurities; Tissue by ferritic phase and volume fraction more than 3.0%, the martensitic phase of less than 10% forms, and described ferritic median size surpasses 6 μ m and below 15 μ m, and the ratio that described martensitic phase exists in the ferrite crystal boundary is more than 90%.
Each described hot-dip galvanizing sheet steel in [1] to [4] as described above wherein, by quality %, contains also that Mo:0.5% is following, V:0.5% is following, B:0.01% is following, Ti:0.1% is following, and following more than one of Nb:0.1%.
Each described hot-dip galvanizing sheet steel in [1] to [5] as described above, wherein, described pot galvanize is alloyed zinc hot dip galvanized.
A kind of method of making hot-dip galvanizing sheet steel, it is characterized in that, the steel that each described one-tenth is grouped in aforementioned to having [1] to [5] carries out melting, carries out hot rolling, cold rolling then, and the gained steel plate is annealed under the annealing temperature more than the Ac1 point, below the Ac3 point.
A kind of method of making hot-dip galvanizing sheet steel, it is characterized in that, in aforementioned to having [1] to [5] each described one-tenth be grouped into and contain volume fraction the hot-rolled steel sheet of the low temperature phase change phase more than 60% carry out cold rolling after, the gained steel plate is annealed under the annealing temperature more than the Ac1 point, below the Ac3 point.
The method of the manufacturing hot-dip galvanizing sheet steel in [7] or [8] wherein, after implementing the pot galvanize processing, is implemented the Alloying Treatment of pot galvanize as described above.
In addition, in this manual, the % of the composition of expression steel is quality %.
According to the present invention, location, distribution and the ratio of weighting content, ferrite median size and martensitic phase by suitably controlling Mn, Cr can access balance and the good hot-dip galvanizing sheet steel of sintering curing of intensity and ductility.And, because it is hot-dip galvanizing sheet steel of the present invention has aforesaid good characteristic, thereby can be widely used in automotive sheet, household electrical appliances etc., useful on industry.
Description of drawings
Fig. 1 is the figure of the relation of expression Mn amount and Cr amount and TS * El.
Fig. 2 is expression Mn and the weighting content of Cr and the figure of the relation between the sintering curing characteristic (BH).
Embodiment
Below the present invention is described in detail.
At first, the restriction reason to the chemical ingredients of the steel among the present invention describes.
C：0.005～0.04％
C is one of element very important among the present invention, makes martensitic phase generate, realize aspect the high strength very effective.But, when C amount surpasses 0.04%, cause processibility significantly to reduce, and also variation of weldability.Therefore, the C amount is made as below 0.04%.On the other hand, from guaranteeing intensity and guarantee the viewpoint that high BH measures that the above martensitic phase of certain volume rate is essential, thereby must contain a certain amount of C.Therefore, the C amount is made as more than 0.005%, preferably is made as above 0.010%.
Below the Si:1.5%
Si is the effective element that obtains high strength and complex tissue for stable.But when the Si amount surpassed 1.5%, surface texture and the chemical transformation property handled significantly reduced.Therefore, the Si amount is made as below 1.5%, preferably is made as below 1.0%.
Mn：1.0～2.0％
Mn is one of element important among the present invention.Generation for martensitic phase is very important element, by improving hardenability and the S in the steel is fixed with MnS, and has the effect of the slab crackle when preventing hot rolling that the embrittlement of grain boundaries with S act as thereby produced.Therefore, must add Mn is more than 1.0%.On the other hand, when interpolation Mn surpasses 2.0%, will cause the remarkable increase of slab cost, and the heavy addition of Mn can promote the formation of banded structure, thereby cause the processibility variation.Therefore, the Mn amount is made as below 2.0%.
Below the P:0.10%
P is to the high strength effective elements.But, when the P amount surpasses 0.10%, the alloying speed of zinc coating is reduced, thereby become the reason that plating is bad or do not plate, simultaneously, the grain boundary segregation of steel plate makes anti-secondary processing brittleness variation.Therefore, the P amount is made as below 0.10%.
Below the S:0.03%
S reduces hot workability, and the thermal crack susceptibility of slab is improved, and when surpassing 0.03%, makes the processibility variation owing to separating out small MnS.Therefore, the S amount is made as below 0.03%.
Al：0.01～0.1％
Al has the effect of the inclusion minimizing that makes in the steel as deoxidant element.But, when Al quantity not sufficient 0.01%, can not stablize the above-mentioned effect that obtains.On the other hand, when the Al amount surpassed 0.1%, bunch shape alumina type inclusion increased, thereby makes the processibility variation.Therefore, the Al amount is made as more than 0.01%, below 0.1%.
N: less than 0.008%
From processibility and ageing viewpoint, the situation that N is few is better.When N amount is 0.008% when above, the generation owing to excessive nitride makes ductility and toughness variation.Therefore, the N amount is made as less than 0.008%.
Cr：0.2～1.0％
Cr is one of element important among the present invention.Cr is the element that hardenability is improved, and adds in order to make stable generation of martensitic phase.Compare with Mn, improve the effect height of hardenability, and because martensitic phase becomes and be easy to exist in crystal boundary, thereby to form for tissue of the present invention be the advantage element.And, because little, the suitable low strength DP steel of solution strengthening energy, thereby be element necessary among the present invention, in order to obtain above-mentioned effect, add more than 0.2%, preferably add more than 0.35%, more preferably interpolation surpasses 0.5%.But, surpass 1.0% even add, because not only its effect is saturated, and form carbide, thereby the ductility variation.Therefore, the Cr amount is made as more than 0.2%, below 1.0%, from the viewpoint of intensity, ductility, preferably is made as more than 0.35%, below 0.8%.
The weighting content of Mn, Cr: 2.1≤Mn (quality %)+1.29Cr (quality %)≤2.8
Mn, Cr are the elements that hardenability is improved, and for martensitic phase is generated its control are become very important in optimal dose.When the weighting insufficient total amount 2.1% of Mn, Cr, becoming is difficult to the BH amount that obtains the DP tissue, can not obtain expecting, thereby strength of parts reduces.And, become high yield ratio, thus punch process itself difficulty that becomes not only, and become and occur shape defect easily.And during cooling behind full annealed, becoming is easy to generate perlite, bainite, thereby BH reduces.On the other hand, surpass under 2.8% the situation in the weighting total amount of Mn, Cr, not only its effect is saturated, and martensite is accompanied by the increase of martensite volume fraction and becomes and be easy to remain in the ferrite crystal grain, thereby plasticity occurs and reduce.And owing to the yield strength of following high strength to increase, press formability significantly reduces as mentioned above, and, cause because the increase of the manufacturing cost that the excessive alloying element of interpolation causes.Therefore, the weighting content Mn+1.29Cr of Mn, Cr is made as 2.1～2.8%, from guaranteeing the viewpoint of high BH, preferably lower limit is made as 2.2%, more preferably lower limit is made as 2.3%.And the viewpoint from excellent formability preferably is made as 2.6% with the upper limit.
Must add element by above, steel of the present invention can access the characteristic as target, still, must add element except above-mentioned, can also add following element as required.
More than one that Mo:0.5% is following, V:0.5% is following, B:0.01% is following, Ti:0.1% is following, Nb:0.1% is following
Below the Mo:0.5%, below the V:0.5%
Mo, V are the elements that improves hardenability, can add for stable generation martensitic phase.But, even excessive interpolation surpasses 0.5%, ductility variation not only, it is unfavorable that the cost aspect also becomes.Therefore, when adding Mo, V, be made as below 0.5% respectively.
Below the B:0.01%
B is the effective element that hardenability is improved, and can obtain martensitic phase and adds for stable.But, even excessive interpolation surpasses 0.01%, can not obtain the effect that matches with cost.Therefore, when adding B, be made as below 0.01%.
Below the Ti:0.1%, below the Nb:0.1%
Thereby Ti, Nb are used to form carbonitride to make solid solution C, N amount reduce, improve the effective element of deep drawing quality.But even all above 0.1% excessive interpolation, because its effect is saturated and the recrystallization temperature in when annealing uprises, thereby manufacturing also reduces.Therefore, when adding Ti, Nb, be made as below 0.1% respectively.
In addition, above-mentioned surplus in addition is made up of Fe and unavoidable impurities.As unavoidable impurities, for example, O can form non-metallic inclusion and bring bad influence to quality, and therefore preferred O is reduced to below 0.003%.
Next, the tissue to hot-dip galvanizing sheet steel of the present invention describes.
Hot-dip galvanizing sheet steel of the present invention by ferritic phase and volume fraction more than 3.0% and the martensitic phase of less than 10% form, and, aforementioned ferritic median size is above 6 μ m and below 15 μ m, and then the ratio that martensitic phase exists in the ferrite crystal boundary is more than 90%.This is the important prerequisite of the present invention, by being made as such tissue, the feasible good hot-dip galvanizing sheet steel of balance that can obtain intensity and ductility in the present invention.
Martensitic phase volume fraction: more than 3.0%, less than 10%
Hot-dip galvanizing sheet steel of the present invention by ferritic phase and volume fraction more than 3.0% and the martensitic phase two-phase structure of less than 10% constitute.When the volume fraction of martensitic phase is 10% when above, automobile inner and outer plates steel plate for panel as object of the present invention, there is not sufficient press formability, therefore preferably the martensitic phase volume fraction is made as less than 10%, from the viewpoint of plasticity, more preferably the martensitic phase volume fraction is made as less than 8%.On the other hand, when the volume fraction less than 3.0% of martensitic phase, the mobile dislocation density of introducing during phase transformation becomes insufficient, thereby BH reduces and shock-resistance reduces.And YP rises, the press formability variation.And then YPE1 becomes and is easy to residually, and the panel surface accuracy reduces.Therefore, the volume fraction with martensitic phase is made as more than 3.0%.
In addition, in the steel plate of the present invention, except ferritic phase and martensitic phase two-phase, perlite phase, bainite phase and then residual γ phase, inevitable carbide are if also can be contained about 3%, but, when perlite and bainite generate near martensite, become the starting point in space easily, and, have the tendency that promotes to grow up in the space, therefore, from the viewpoint of plasticity, preferably perlite phase, bainite phase and then residual γ phase, inevitable carbide are made as less than 1.5%, are more preferably below 1.0%.
Ferrite median size: above 6 μ m and below 15 μ m
The crystallization particle diameter is more small, and the effective n value of stretch forming or uniform elongation are more reduced, and when the ferrite median size is 6 μ m when following, the reduction of n value and uniform elongation is remarkable.On the other hand, when the ferrite median size surpasses 15 μ m, can cause surface irregularity etc. during drawing, thereby make the surface texture variation, thus not preferred.Therefore, the ferrite particle diameter is made as above 6 μ m and below 15 μ m.
The position that martensitic phase exists: in the ferrite crystal boundary more than 90%
The position that martensitic phase exists is extremely important in the present invention, is be used to the important prerequisite that obtains effect of the present invention.The ferritic phase-change energy of the martensite mutual-assistance that exists in the ferrite crystal grain reduces, when the ratio of the martensitic phase that exists in the ferrite crystal grain 10% when above, it is remarkable that this tendency becomes.Therefore, in order to obtain as the good intensity of target of the present invention and the balance of ductility, what must make martensitic phase occupies the ferrite crystal boundary more than 90%.In addition, be more than 95% for the ratio that obtains more good intensity and the balance of ductility, be more preferably to exist in the ferrite crystal boundary.
Next, balance and good the creating conditions of hot-dip galvanizing sheet steel of sintering curing to intensity of the present invention and ductility describes.
Hot-dip galvanizing sheet steel of the present invention is characterised in that, the steel that is adjusted into aforementioned chemical ingredients scope is carried out melting, then, carries out cold rollingly after hot rolling, and will anneal in the temperature range of gained steel plate more than the Ac1 point, below the Ac3 point.At this moment, preferably carry out cold rolling to containing volume fraction at the hot-rolled steel sheet of the low temperature phase change phase more than 60%.
And, when the pot galvanize of hot-dip galvanizing sheet steel of the present invention after annealing handled, under the annealing temperature more than the Ac1 point, below the Ac3 point, carry out full annealed, then, from annealing temperature to the pot galvanize treatment temp with average cooling rate surpass 3 ℃/s and 15 ℃/ once cool off below the s, more preferably with 5 ℃ of average cooling rates/carry out more than s secondary cooling.Perhaps, after the zinc-plated processing of aforementioned hot, also can carry out the Alloying Treatment of coating.Thisly can in the continuous hot galvanizing operating line, carry out carrying out the operation that pot galvanize handles after the annealing.
Below, to the optimum condition of hot-rolled steel sheet tissue, creating conditions is elaborated.
Hot-rolled steel sheet tissue: the low temperature phase change phase (preferable range) more than 60%
In above-mentioned operation, as the hot-rolled steel sheet of gained after the enforcement hot rolling, the tissue that preferably has the low temperature phase change phase that contains more than 60%.Under the situation of the hot-rolled steel sheet of the tissue that was in the past constituted mutually by ferritic phase+perlite, the insolubles that when the two phase regions annealing of α+γ, has carbide easily, and, the distribution of the perlite phase of reflect heat rolled steel plate and become the state of the thick mutually inhomogeneous existence of γ.The result has formed the tissue of being made up of the martensitic phase of thicker and inhomogeneous dispersion.On the other hand, as the present invention, containing volume fraction under the situation of the hot-rolled steel sheet of the low temperature phase change phase more than 60%, in the temperature-rise period when annealing, fine carbide temporarily is dissolved in the ferritic phase, and when the annealing of two phase regions of α+γ, generate fine γ phase equably by the crystal boundary of ferritic phase.Think that consequently as purpose of the present invention, martensitic phase is dispersed in the ferrite crystal boundary, and the local elongation rate increases.In addition, the low temperature phase change of hot-rolled steel sheet refers to acicular ferrite phase, bainite ferrite phase, bainite phase, martensitic phase and their mixed phase mutually.And, hot-rolled steel sheet with the low temperature phase change phase more than 60% can or suppress its growth by the ferrite transformation after the finish to gauge and obtain, for example, can by after the finish to gauge with 50 ℃/cool off more than the s, when suppressing ferrite transformation, coiling temperature be made as below 600 ℃ and obtain.Preferred coiling temperature is 550 ℃ of less thaies.
Rate of heating: ℃ to the temperature range of annealing temperature, be made as 10 ℃/s of less than (preferable range) from Ac1 transformation temperature-50
Though the rate of heating when being not particularly limited full annealed, in order to be easy to obtain the steel plate tissue (position that ferrite median size, martensitic phase exist) as target of the present invention, preferred recrystallization is fully finished the back above the Ac1 transformation temperature.Therefore, for example, ℃ to the temperature range of annealing temperature, preferably be made as 10 ℃/s of less than from Ac1 transformation temperature-50.In addition, be lower than a side of this temperature range, need not be made as the slow heating of 10 ℃/s of less than, can be made as rapid heating.And, containing volume fraction under the situation of the hot-rolled steel sheet of the low temperature phase change phase more than 60%, must obtain tissue of the present invention more effectively.
Annealing temperature: more than the Ac1 point, below the Ac3 point
In order to obtain little tissue of ferritic phase+martensitic phase, annealing temperature must be heated to suitable temperature.When annealing temperature deficiency Ac1 point, can not generate the austenite phase, and can not obtain martensitic phase.And, the miniaturization of ferrite particle diameter, thus press formability is along with n value and uniform elongation reduce and reduce sometimes.On the other hand, when annealing temperature surpasses the Ac3 point, the whole austenitizings of ferritic phase, thereby the characteristic variation such as plasticity that obtained by recrystallization.And, cause thickization of ferrite particle diameter, surface texture variation.And, therefore insufficient to the C multiviscosisty of γ in mutually when high temperature annealing because C amount is suppressed in lower concentration in steel of the present invention, thus be difficult to obtain the DP tissue, and intensity and BH amount reduce.And even obtain under the situation of DP tissue fully improving hardenability, martensite is also separated out in a large number at intragranular, thereby ductility reduces.Therefore, annealing temperature is made as the Ac1 point, below the Ac3 point.From the viewpoint of plasticity, be made as preferably that the Ac1 point is above, below Ac1 point+100 ℃.And, promote to the viewpoint of the element multiviscosisty of austenite phase when obtaining preferred ferrite median size, be made as annealing time more than 15 seconds and less than 60 seconds.In addition, though Ac1, Ac3 point can be tried to achieve by actual measurement, also can calculate by following formula (" Lesley (leslie) ferrous materials ", P.273, the kind Co., Ltd. of ball).
Ac1＝723-10.7Mn+29.1Si+16.9Cr
Ac3＝910-203C^0.5+44.7Si+104V+31.5Mo-30Mn-11Cr+700P+400A1+400Ti
A speed of cooling: surpass 3 ℃/s and 15 ℃/(preferable range) below the s
When making hot-dip galvanizing sheet steel, though be not particularly limited a speed of cooling of handling from annealing temperature to hot dip, the viewpoint that forms from martensite is preferably to surpass 3 ℃/s and to cool off at 15 ℃/ average cooling rate below the s.When speed of cooling surpasses 3 ℃/s, in process of cooling, suppress austenite to pearlitic phase transformation, becoming as the martensitic phase of target of the present invention is easy to form, and the balance of intensity and ductility and sintering curing raising.And, when speed of cooling 15 ℃/when s is following, can the plate of steel plate laterally, vertically (direction of passage) more stably obtain target steel plate tissue of the present invention, thereby preferably.Therefore, preferred annealing temperature to the average cooling rate of plating temperature for surpass 3 ℃/s and 15 ℃/below the s.And, when average cooling rate is made as 5 ℃/more than the s, 15 ℃/be effective when s is following.In addition, the plating temperature can be common about 400～480 ℃.
Secondary speed of cooling: 5 ℃/s above (preferable range)
Secondary cooling after pot galvanize handled the back or further implement the Alloying Treatment of pot galvanize needn't limit especially, but 5 ℃/when s is above, suppress austenite to the phase transformation of perlite etc., the formation easily thereby martensitic phase becomes.Therefore, preferably the secondary speed of cooling is made as 5 ℃/more than the s.On the other hand, though needn't limit especially the upper limit of secondary speed of cooling, for example from the viewpoint of suppressing plate shape variation, be preferably 100 ℃/s of less than.In addition, as long as the Alloying Treatment of pot galvanize is usually in heating about 500～700 ℃, under preferred about 550～600 ℃ temperature and keep about several seconds to tens seconds.
As other conditions, the melting method of steel is not particularly limited, can be electric furnace, also can be converter.And the castmethod of the steel after the melting can be to form cast panel by continuous metal cast process, also can be to form steel ingot by ingot casting method.When behind continuous casting, slab being carried out hot rolling, can in process furnace, be rolled behind the reheat, perhaps also can not heat carry out directly rolling.In addition, also can behind ingot casting, carry out split rolling method for hot rolling.And, when the hot rolling finishing temperature is implemented relatively good when the Ar3 point is above.For cold rolling rate, preferably be made as in 50～85% the common operating restraint.
As the pot galvanize condition, weight per unit area is preferably 20～70g/m 2, the Fe% in the coating is preferably 6～15%.
In addition, in the present invention, for the shape correction after the thermal treatment, also can carry out temper rolling to steel plate of the present invention.And among the present invention, imagination is made the situation of steel billet through common steel processed, casting, each operation of hot rolling, but also can by clipped such as for example sheet blank continuous casting or all hot-rolled process make.
And, the steel plate that obtains according to above explanation is implemented the electro-galvanizing class also must access target effect.And, also can behind plating, further implement organic envelope to these plated steel sheets and handle.
Embodiment
Below, be further detailed by the present invention of embodiment.
With the steel that the vacuum melting melting has the chemical ingredients of the A～Y of steel shown in the table 1, make slab by continuous casting then.Steel A～S is example of the present invention, and steel T and U are the comparative example of C amount outside the scope of the invention, and steel V, X and Y are the comparative example of weighting content outside the scope of the invention of Mn and Cr, and steel W is Mn amount and the comparative example of Cr amount outside the scope of the invention.
The slab that as above makes is heated under 1200 ℃, under the temperature more than the Ar3 point, carry out finish to gauge then, then, after the enforcement water-cooled, under the temperature that surpasses 650 ℃ of 500 ℃ and less thaies, batch, make the volume fraction of low temperature phase change phase at the hot-rolled steel sheet of 5～100% variations.
After the hot-rolled steel sheet enforcement pickling to gained, carry out cold bundle under 75% rolling rate, making thickness is the cold bundle steel plate of 0.75mm.
The sample that will downcut from the cold bundle steel plate of gained is in the infrared rays image furnace, rate of heating with 5～20 ℃/s as shown in table 2 ℃ is heated to annealing temperature from Ac1 transformation temperature-50, and under the annealing temperature shown in the table 2, kept 30 seconds, then, a speed of cooling with 3～20 ℃/s is cooled off, and impregnated in and implement pot galvanize in 460 ℃ the plating bath and handle.And then carry out Alloying Treatment with 550 ℃ * 15 seconds, and then, cool off with the secondary speed of cooling of 4～20 ℃/s, obtain alloyed hot-dip galvanized steel sheet.
Then, from the alloyed hot-dip galvanized steel sheet collected specimens that as above obtains, according to following method, the crystal boundary of the second phase volume rate beyond the volume fraction of ferrite median size, martensitic phase, the martensitic phase and martensitic phase is separated out ratio measure, and carry out mechanical characteristics and BH and measure and be used for performance evaluation.
The patterning method that the ferrite median size is put down in writing according to JIS G 0552, measured by the opticmicroscope tissue (400 times) at the thickness of slab of sample central authorities section place.
It is to polish at the thickness of slab section to sample, after the nital corrosion, use little tissue of being taken by scanning electronic microscope (SEM) to measure that the second phase volume rate beyond the volume fraction of martensitic phase, martensitic phase and the crystal boundary of martensitic phase are separated out ratio.Wherein, these mensuration are that the continuous tissue ground of indulging 100 μ m * horizontal 200 μ m visuals field to the thickness of slab central part is observed under 2000 times multiplying power, and try to achieve mean value.
Mechanical characteristics is after gathering the JIS5 test film, test method according to regulation among the JIS Z 2241 is carried out tension test, thereby measures mechanical characteristics (YP: yield strength, TS: tensile strength, T-EI: full elongation, U-EI: uniform elongation, L-EI: the local elongation rate).
BH amount is after gathering the JIS5 test film, according to the method for regulation among the JIS G 3135, appends 2% prestrain, implements 170 ℃ * 20 minutes thermal treatment then, and afterwards, the increasing amount of the yield strength when carrying out tension test is again estimated.
In addition, in the present invention, TS * El is made as more than the 16000MPa*%, is preferably more than the 16500MPa*%, more preferably more than the 17000MPa*%.And, the BH amount is made as more than the 50MPa, be preferably more than the 55MPa, more preferably more than the 60MPa.Guarantee the viewpoint of essential anti-stampability when the steel plate that is applied to the automobile exterior panel panel is carried out lightweight by thin-walled property, this is essential BH amount.
Merge above result and create conditions and be shown in table 2.
In table 2, sample No.1,4,5,7～13,15,17～35,37,38 composition and create conditions within the scope of the present invention, be have the martensitic phase volume fraction more than 3.0% and less than 10%, ferrite median size surpass 6 μ m and below 15 μ m and the ratio that in the ferrite crystal boundary, exists of martensitic phase in the example of the present invention of the tissue more than 90%.As can be known by example of the present invention, can obtain TS * El more than the 16000MPa*% and the BH amount more than 50MPa, balance and the good hot-dip galvanizing sheet steel of sintering curing of intensity and ductility.On the other hand, sample No.39, the 40th, the comparative example of C amount outside the scope of the invention, sample No.41,43, the 44th, the comparative example of weighting content outside the scope of the invention of Mn and Cr, sample No.42 is Mn amount and the comparative example of Cr amount outside the scope of the invention, sample No.2,3,6,14,16, the 36th, the comparative example of annealing temperature outside the scope of the invention, more than any one in the ratio that the volume fraction of martensitic phase, ferrite median size, martensitic phase exist in the ferrite crystal boundary outside the scope of the invention.Think that this result is, because TS * El is relatively poor, thereby press formability is insufficient, and, because the BH amount is relatively poor, thereby be difficult to than in the past steel plate thin-walled property more.
And, when the identical and hot-rolled sheet of composition being organized different sample No.1 and 4,5 and 7,10 and 11,25～27 example of the present invention compare, the ratio of the low temperature phase change phase in the hot-rolled sheet tissue is compared with sample No.4,11,27 example of the present invention at the sample No.1,5,7,10,25 of the preferable range more than 60%, 26 as can be known, and the balance of intensity and ductility improves.And, as the sample No.5 and 9,10 and 12 that rate of heating is different to composition is identical, composition is identical and sample No.5 and 8,32 and 35 that annealing temperature is different, identical and different No.32～34 of speed of cooling of composition, composition is identical and No.25,28 that the secondary speed of cooling is different, when 29 example of the present invention compares, rate of heating is at the sample No.7,10 of the preferable range of 10 ℃/s of less than as can be known, and annealing temperature is at Ac 1The sample No.5,32 of the preferable range below point+100 ℃, speed of cooling is surpassing 3 ℃/s and at the sample No.32 of 15 ℃/ preferable range below the s, the secondary speed of cooling is at the sample No.25,29 of 5 ℃/ preferable range more than the s, compare with No.9,12,8,35,33,34,28 example of the present invention, the balance of intensity and ductility improves.
And, result based on table 2, outside the sample No.39,40 of C amount the scope of the invention, for having 100% low temperature phase change as the hot-rolled sheet tissue, and the sample No.1,5,10,13,15,17～25,30～32,37,38 with various Mn, Cr amount in preferable range of the present invention of Heating temperature, annealing temperature, speed of cooling, secondary speed of cooling, 41～44 example of the present invention and comparative example, will put that Mn amount and Cr measure and the relation of TS * El the results are shown in Fig. 1.According to Fig. 1 as can be known, example of the present invention has the above TS * El of 16000MPa*%, and in the example of the present invention in the weighting content of Mn and Cr is 2.2～2.6% preferable range, TS * El is more than 16500MPa*%, and the balance of intensity and ductility is good.And, being 0.35～0.8% in Cr amount as can be known, in the example of the present invention in the more preferably scope of weighting content 2.3～2.6% of Mn and Cr, TS * El is more than the 17000MPa*%, the balance of intensity and ductility is better.
And, about above-mentioned steel, for the arrangement result of the relation of the weighting content of Mn and Cr and BH amount as shown in Figure 2.According to Fig. 2 as can be known, the weighting content of Mn and Cr is measured at the BH that the example of the present invention more than 2.1% has more than the 50MPa, in the following preferable range that is limited to more than 2.2% of the weighting content of Mn and Cr for more than the 55MPa, for more than the 60MPa, the sintering curing characteristic is good in the following more preferably scope that is limited to more than 2.3% of the weighting content of Mn and Cr.
Utilize possibility on the industry
Hot-dip galvanizing sheet steel of the present invention because balance and the sintering curing characteristic good of intensity and ductility, thereby can be applied to have the parts of high formability, is used for the automobile inner and outer plates from needless to say, more preferably is used for requiring the field of high formability.And, when hot-dip galvanizing sheet steel of the present invention is used for the automobile inner and outer plates, also can realize lightweight by thin-walled property.
Figure S2006800465568D00201
Figure S2006800465568D00211
Figure S2006800465568D00221

Claims (9)

1. hot-dip galvanizing sheet steel, it is characterized in that, having following one-tenth is grouped into: by quality %, contain that C:0.005～0.04%, Si:1.5% are following, Mn:1.0～2.0%, P:0.10% is following, S:0.03% is following, Al:0.01～0.1%, N: less than 0.008% and Cr:0.2～1.0%, and satisfy 2.1≤Mn (quality %)+1.29Cr (quality %)≤2.8, surplus is made up of iron and unavoidable impurities; Tissue by ferritic phase, volume fraction more than 3.0% and the martensitic phase of less than 10% and volume fraction less than 1.5% and do not comprise 0 perlite phase, bainite phase, residual γ phase, inevitably carbide is formed, and described ferritic median size surpasses 6 μ m and below 15 μ m, and the ratio that described martensitic phase exists in the ferrite crystal boundary is more than 90%.
2. hot-dip galvanizing sheet steel, it is characterized in that, having following one-tenth is grouped into: by quality %, contain that C:0.005～0.04%, Si:1.5% are following, Mn:1.0～2.0%, P:0.10% is following, S:0.03% is following, Al:0.01～0.1%, N: less than 0.008% and Cr:0.2～1.0%, and satisfy 2.2≤Mn (quality %)+1.29Cr (quality %)≤2.8, surplus is made up of iron and unavoidable impurities; Tissue by ferritic phase, volume fraction more than 3.0% and the martensitic phase of less than 10% and volume fraction less than 1.5% and do not comprise 0 perlite phase, bainite phase, residual γ phase, inevitably carbide is formed, and described ferritic median size surpasses 6 μ m and below 15 μ m, and the ratio that described martensitic phase exists in the ferrite crystal boundary is more than 90%.
3. hot-dip galvanizing sheet steel, it is characterized in that, having following one-tenth is grouped into: by quality %, contain that C:0.005～0.04%, Si:1.5% are following, Mn:1.0～2.0%, P:0.10% is following, S:0.03% is following, Al:0.01～0.1%, N: less than 0.008% and Cr:0.2～1.0%, and satisfy 2.3≤Mn (quality %)+1.29Cr (quality %)≤2.8, surplus is made up of iron and unavoidable impurities; Tissue by ferritic phase, volume fraction more than 3.0% and the martensitic phase of less than 10% and volume fraction less than 1.5% and do not comprise 0 perlite phase, bainite phase, residual γ phase, inevitably carbide is formed, and described ferritic median size surpasses 6 μ m and below 15 μ m, and the ratio that described martensitic phase exists in the ferrite crystal boundary is more than 90%.
4. hot-dip galvanizing sheet steel, it is characterized in that, having following one-tenth is grouped into: by quality %, contain that C:0.005～0.04%, Si:1.5% are following, Mn:1.0～2.0%, P:0.10% is following, S:0.03% is following, Al:0.01～0.1%, N: less than 0.008% and Cr:0.35～0.8%, and satisfy 2.3≤Mn (quality %)+1.29Cr (quality %)≤2.8, surplus is made up of iron and unavoidable impurities; Tissue by ferritic phase, volume fraction more than 3.0% and the martensitic phase of less than 10% and volume fraction less than 1.5% and do not comprise 0 perlite phase, bainite phase, residual γ phase, inevitably carbide is formed, and described ferritic median size surpasses 6 μ m and below 15 μ m, and the ratio that described martensitic phase exists in the ferrite crystal boundary is more than 90%.
5. according to each described hot-dip galvanizing sheet steel in the claim 1 to 4, wherein, by quality %, contain also that Mo:0.5% is following, V:0.5% is following, B:0.01% is following, Ti:0.1% is following, and following more than one of Nb:0.1%.
6. according to each described hot-dip galvanizing sheet steel in the claim 1 to 5, wherein, described pot galvanize is alloyed zinc hot dip galvanized.
7. method of making hot-dip galvanizing sheet steel, it is characterized in that, each described one-tenth is grouped in the claim 1 to 5 to having, and carry out hot rolling, cold rolling gained steel plate, be heated to the average rate of heating of 10 ℃/s of less than be lower than 50 ℃ of Ac1 transformation temperatures temperature to more than the Ac1 point, the temperature province of the annealing temperature that the Ac3 point is following, and to anneal under the described annealing temperature, afterwards to surpass 3 ℃/s and to cool off at 15 ℃/ average cooling rate below the s, and be impregnated into after the zinc-plated bath, perhaps, further carry out zinc-plated Alloying Treatment after being impregnated into described zinc-plated bath after, the average cooling rate above with 5 ℃/s cools off.
8. method of making hot-dip galvanizing sheet steel, it is characterized in that, each described one-tenth is grouped in the claim 1 to 5 to having, and contain volume fraction the hot-rolled steel sheet of the low temperature phase change phase more than 60% carry out cold rolling after, to the gained steel plate be heated to the average rate of heating of 10 ℃/s of less than be lower than 50 ℃ of Ac1 transformation temperatures temperature to more than the Ac1 point, the temperature province of the annealing temperature that the Ac3 point is following, and to anneal under the described annealing temperature, afterwards to surpass 3 ℃/s and to cool off at 15 ℃/ average cooling rate below the s, and be impregnated into after the zinc-plated bath, perhaps, further carry out zinc-plated Alloying Treatment after being impregnated into described zinc-plated bath after, the average cooling rate above with 5 ℃/s cools off.
9. according to the method for claim 7 or 8 described manufacturing hot-dip galvanizing sheet steels, wherein, after implementing the pot galvanize processing, implement the Alloying Treatment of pot galvanize.
CN200680046556.8A 2006-01-11 2006-12-25 Hot-dip zinc-coated steel sheets and process for production thereof Expired - Fee Related CN101326300B (en)

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